Familial hemiplegic migraine in Indian children-a tertiary center experience

Familial hemiplegic migraine (FHM), an autosomal dominant subtype of hemiplegic migraine, is a channelopathy presenting with severe headache, visual field defect, paresthesia, unilateral motor deficit, encephalopathy, seizures and aphasia. This cross-sectional study was conducted over 10 months in children aged 1-18 years suspected of hemiplegic migraine at a tertiary care pediatric hospital. Fourteen children were screened and five children with genetically confirmed FHM were included. The symptoms in the study population were paroxysmal hemiparesis (5/5), headache (5/5) and focal seizures (1/5). The hemiplegia episodes lasted from 4 h to 7 days. The mean age at the onset of neurological symptoms was 6.8 ± 0.7 years and the mean age at diagnosis was 12.8 ± 1.7 years, with a mean delay of 6.1 ± 1.9 years for the diagnosis. Neuroimaging during acute episodes revealed accentuated gray, white differentiation in the contralateral cerebral hemisphere with mild effacement of sulcal spaces in T2/fluid-attenuated inversion recovery (FLAIR) images. Genetic testing revealed ATP1A2 mutations (FHM2) in 4/5 and SCN1A (FHM3) in 1/5 patients. All of them (5/5) were initiated on oral topiramate and had favorable treatment responses with a mean follow-up duration of 7 ± 1.4 months. Diagnosis of FHM is mainly clinical and can be confirmed by genetic analysis. Perfusion and diffusion-weighted MRI should be considered during acute headache episodes, as it is mostly normal in symptom-free periods. Routine MRI sequences like T1 weighted, T2 weighted, FLAIR and contrast remain normal even during acute attacks.

Exome sequencing of ATP1A3-negative cases of alternating hemiplegia of childhood reveals SCN2A as a novel causative gene

Alternating hemiplegia of childhood (AHC) is a rare neurodevelopment disorder that is typically characterized by debilitating episodic attacks of hemiplegia, seizures, and intellectual disability. Over 85% of individuals with AHC have a de novo missense variant in ATP1A3 encoding the catalytic α3 subunit of neuronal Na+/K+ ATPases. The remainder of the patients are genetically unexplained. Here, we used next-generation sequencing to search for the genetic cause of 26 ATP1A3-negative index patients with a clinical presentation of AHC or an AHC-like phenotype. Three patients had affected siblings. Using targeted sequencing of exonic, intronic, and flanking regions of ATP1A3 in 22 of the 26 index patients, we found no ultra-rare variants. Using exome sequencing, we identified the likely genetic diagnosis in 9 probands (35%) in five genes, including RHOBTB2 (n = 3), ATP1A2 (n = 3), ANK3 (n = 1), SCN2A (n = 1), and CHD2 (n = 1). In follow-up investigations, two additional ATP1A3-negative individuals were found to have rare missense SCN2A variants, including one de novo likely pathogenic variant and one likely pathogenic variant for which inheritance could not be determined. Functional evaluation of the variants identified in SCN2A and ATP1A2 supports the pathogenicity of the identified variants. Our data show that genetic variants in various neurodevelopmental genes, including SCN2A, lead to AHC or AHC-like presentation. Still, the majority of ATP1A3-negative AHC or AHC-like patients remain unexplained, suggesting that other mutational mechanisms may account for the phenotype or that cases may be explained by oligo- or polygenic risk factors.

Characteristics of non-sleep related apneas in children with alternating hemiplegia of childhood

BACKGROUND

Non-sleep related apnea (NSA) has been observed in alternating hemiplegia of childhood (AHC) but has yet to be characterized.

GOALS

Investigate the following hypotheses: 1) AHC patients manifest NSA that is often severe. 2) NSA is usually triggered by precipitating events. 3) NSA is more likely in patients with ATP1A3 mutations.

METHODS

Retrospective review of 51 consecutive AHC patients (ages 2-45 years) enrolled in our AHC registry. NSAs were classified as mild (not needing intervention), moderate (needing intervention but not perceived as life threatening), or severe (needing intervention and perceived as life threatening).

RESULTS

19/51 patients (37 %) had 52 NSA events (6 mild, 11 moderate, 35 severe). Mean age of onset of NSA (± Standard Error of the Mean (SEM)): 3.8 ± 1.5 (range 0-24) years, frequency during follow up was higher at younger ages as compared to adulthood (year 1: 2.2/year, adulthood: 0.060/year). NSAs were associated with triggering factors, bradycardia and with younger age (p < 0.008 in all) but not with mutation status (p = 0.360). Triggers, observed in 17 patients, most commonly included epileptic seizures in 9 (47 %), anesthesia, AHC spells and intercurrent, stressful, conditions. Management included use of pulse oximeter at home in nine patients, home oxygen in seven, intubation/ventilatory support in seven, and basic CPR in six. An additional patient required tracheostomy. There were no deaths or permanent sequalae.

CONCLUSIONS

AHC patients experience NSAs that are often severe. These events are usually triggered by seizures or other stressful events and can be successfully managed with interventions tailored to the severity of the NSA.

Precision therapy for a medically actionable ATP1A3 variant from a genomic medicine program in an underserved population

BACKGROUND

Genomic medicine is revolutionizing the diagnosis of rare diseases, but the implementation has not benefited underrepresented populations to the same degree. Here, we report the case of a 7-year-old boy with hypotonia, global developmental delay, strabismus, seizures, and previously suspected mitochondrial myopathy. This proband comes from an underrepresented minority and was denied exome sequencing by his public insurance.

METHODS

After informed consent was obtained, buccal cells from the proband were collected and whole exome sequencing was performed. Illumina Dragen and Emedgene software was used to analyze the data at Baylor Genetics. The variants were further intepreted according to ACMG guidelines and the patient's phenotype.

RESULTS

Through whole-exome sequencing (WES) under the Community Texome project, he was found to have a heterozygous de novo pathogenic variant in the ATP1A3 gene located on chromosome 19q13.

CONCLUSION

In retrospect, his symptomatology matches the known medical conditions associated with the ATP1A3 gene namely Alternating Hemiplegia of Childhood 2 (AHC), a rare autosomal dominant disorder with an incidence of 1 in one million. His single nucleotide variant, (c.2401G>A, p.D801N), is predicted to be damaging. The specific amino acid change p.D801N has been previously reported in ClinVar along with the allelic variant p.D801Y and both are considered pathogenic. The identification of this variant altered medical management for this patient as he was started on a calcium antagonist and has reported no further hemiplegic episodes. This case illustrates the value of implementing genomic medicine for precision therapy in underserved populations.

Multidisciplinary team collaboration impact on NGF, BDNF, serum IGF-1, and life quality in patients with hemiplegia after stroke

This study aimed to study the impact of multidisciplinary team collaboration on NGF, BDNF, serum IGF-1, and life quality in patients with hemiplegia after stroke. For this purpose, 200 post-stroke hemiplegic patients admitted from March 2022 to February 2023 were selected and randomly divided into a control group (100) and an observation group (100). The control group was given routine nursing care, while the observation group was given a multidisciplinary team collaboration model. The neurotroph in [nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), insulin-like growth factor-1 (IGF-1)] and nutritional status [hemoglobin (HGB), serum albumin (ALB), transferrin (TRF)] of patients were compared before and after the intervention on the second day of admission and on the 30th day of intervention. The FUGL Meyer (FM) motor function assessment scale, NIHSS National Institutes of Health Stroke Scale, and the Specialized Quality of Life Scale (SS-QIL) for stroke patients were used to assess limb motor function, balance function, degree of neurological impairment, and life quality. Results showed that before intervention, there was no statistically significant difference in the levels of NGF, BDNF, IGF-1, HGB, ALB, TRF, limb motor function, balance function, neurological deficits, and quality of life scores between the two (P>0.05); After intervention, the levels of NGF, BDNF, IGF-1, HGB, ALB, and TRF in the observation group were significantly higher (P<0.05); The FM and SS-QOL of patients in the observation group were significantly higher (P<0.05); The NIHSS score of patients in the observation group was significantly lower (P<0.05). In conclusion, multidisciplinary team cooperation can significantly improve the level of neurotrophin, reduce the degree of nerve defect, and promote the recovery of limb function, balance function and life quality for stroke patients with hemiplegia.

The clinical spectrum associated with ATP1A2 variants in Chinese pediatric patients

PURPOSE

To evaluate the clinical spectrum associated with ATP1A2 variants in Chinese children with hemiplegia, migraines, encephalopathy or seizures.

METHODS

Sixteen children (12 males and 4 females), including ten patients with ATP1A2 variants whose cases had been published previously, were identified using next-generation sequencing.

RESULTS

Fifteen patients had FHM2 (familial hemiplegic migraine type 2), including three who had AHC (alternating hemiplegia of childhood) and one who had drug-resistant focal epilepsy. Thirteen patients had DD (developmental delay). The onset of febrile seizures, which occurred between 5 months and 2 years 5 months (median 1 year 3 months) was earlier than the onset of HM (hemiplegic migraine), which occurred between 1 year 5 months and 13 years (median 3 years 11 months). Disturbance of consciousness subsided first, at 40 h to 9 days (median 4.5 days); hemiplegia and aphasia were resolved slowly, taking 30 min to 6 months (median 17.5 days) for the former and 24 h to over 1 year (median 14.5 days) for the latter. Cranial MRI showed edema in the cerebral hemispheres, mainly the left hemisphereacute attacks. All thirteen FHM2 patients recovered to baseline in 30 min to 6 months. Fifteen patients had between 1 and 7 (median 2) total attacks between the baseline and follow-up timepoints. We report twelve missense variants, including a novel variant ATP1A2 variant, p.G855E.

CONCLUSIONS

The known genotypic and phenotypic spectra of Chinese patients with ATP1A2-related disorders were further expanded. Recurrent febrile seizures and DD combined with paroxysmal hemiplegia and encephalopathy should raise the clinical suspicion of FHM2. The avoidance of triggers and thus the prevention of attacks may be the most effective therapy for FHM2.

Epilepsy with eyelid myoclonia in the setting of de novo pathogenic variant in ATP1A3

Mutations in the ATP1A3 gene have been associated with several syndromes, including rapid-onset dystonia-parkinsonism, alternating hemiplegia of childhood, and cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss. In this clinical commentary, we report a 2-year-old female patient with de novo pathogenic variant in the ATP1A3 gene associated with an early-onset form of epilepsy with eyelid myoclonia. The patient had frequent eyelid myoclonia occurring 20-30 times per day, without loss of awareness or other motor manifestations. EEG showed generalized polyspikes and spike-and-wave complexes maximal in the bifrontal regions, with prominent eye closure sensitivity. A sequencing-based epilepsy gene panel revealed a de novo pathogenic heterozygous variant in ATP1A3. The patient showed some response to flunarizine and clonazepam. This case highlights the importance of considering ATP1A3 mutations in the differential diagnosis of early-onset epilepsy with eyelid myoclonia and the potential benefit of flunarizine in improving language and coordination development in patients with ATP1A3-related disorders.

Expanding the Allelic spectrum in ATP1A3-related disorders with 3 novel mutations and clinic features

OBJECTIVES

To describe the complex phenotype of ATP1A3 and second to report new mutation of ATP1A3.

METHODS

This is a retrospective chart review of 7 patients who was diagnosed with ATP1A3 mutation based on whole exome sequencing (WES) result and the following information were collected; age, age of onset, developmental ability, seizure type, family history, MRI, WES report. The data collection started a year ago January 2021 in King Faisal Specialist Hospital and Research Centre, Riyadh, KSA. This has been cleared for publication by the Office of Research Affairs, and the Publication Number is 2225429.

RESULTS

Five females and 2 males had onset ages of 0-3 years (mean=18 months). All had some degree of intellectual dysfunction, 6 had seizures (85%), 4 had neurologic abnormalities, 1 had autistic features and one had mild dystonia.

CONCLUSION

Our small-cohort observations confirm that ATP1A3 mutations express a wide range of phenotypes, usually including some degree of cognitive-behavioral dysfunction (100% of patients), seizures (85% of patients), and AHC (71% of patients). Moreover, they further expand the evolving allelic spectrum of these disorders by identifying 3 novel mutations.

Alternating hemiplegia of childhood

Alternating hemiplegia of childhood (AHC) is characterized by recurrent episodes of hemiplegia which may alternate sides between attacks. The condition is associated with severe neurodevelopmental disorder presenting in early infancy, and may encompass a wide range of other paroxysmal manifestations (e.g., dystonia, nystagmus, dysautonomia) and pervasive neurological disabilities (e.g., developmental delay, learning disabilities, choreoathetosis, and ataxia). Epileptic seizures are particularly common among patients with AHC. Diagnosis is usually based on history and clinical grounds using the Aicardi criteria. Mutations in the ATP1A3 gene are implicated in the disease pathology of the condition, as well as several other neurodevelopmental disorders, suggesting AHC forms part of a spectrum of overlapping clinical syndromes rather than a distinct clinical entity per se. Management of patients with AHC includes the rapid induction of sleep during paroxysmal attacks and the avoidance of identified triggers. Pharmacotherapeutic treatments have a role in managing epileptic seizures, as well as in the prevention of paroxysmal attacks wherein flunarizine remains the treatment of choice.

The Phenotypic Continuum of ATP1A3-Related Disorders

BACKGROUND AND OBJECTIVES

ATP1A3 is associated with a broad spectrum of predominantly neurologic disorders, which continues to expand beyond the initially defined phenotypes of alternating hemiplegia of childhood, rapid-onset dystonia parkinsonism, and cerebellar ataxia, areflexia, pes cavus, optic atrophy, sensorineural hearing loss syndrome. This phenotypic variability makes it challenging to assess the pathogenicity of an ATP1A3 variant found in an undiagnosed patient. We describe the phenotypic features of individuals carrying a pathogenic/likely pathogenic ATP1A3 variant and perform a literature review of all ATP1A3 variants published thus far in association with human neurologic disease. Our aim is to demonstrate the heterogeneous clinical spectrum of the gene and look for phenotypic overlap between patients that will streamline the diagnostic process.

METHODS

Undiagnosed individuals with ATP1A3 variants were identified within the cohort of the Deciphering Developmental Disorders study with additional cases contributed by collaborators internationally. Detailed clinical data were collected with consent through a questionnaire completed by the referring clinicians. PubMed was searched for publications containing the term "ATP1A3" from 2004 to 2021.

RESULTS

Twenty-four individuals with a previously undiagnosed neurologic phenotype were found to carry 21 ATP1A3 variants. Eight variants have been previously published. Patients experienced on average 2-3 different types of paroxysmal events. Permanent neurologic features were common including microcephaly (7; 29%), ataxia (13; 54%), dystonia (10; 42%), and hypotonia (7; 29%). All patients had cognitive impairment. Neuropsychiatric diagnoses were reported in 16 (66.6%) individuals. Phenotypes were extremely varied, and most individuals did not fit clinical criteria for previously published phenotypes. On review of the literature, 1,108 individuals have been reported carrying 168 different ATP1A3 variants. The most common variants are associated with well-defined phenotypes, while more rare variants often result in very rare symptom correlations, such as are seen in our study. Combined Annotation-Dependent Depletion (CADD) scores of pathogenic and likely pathogenic variants were significantly higher and variants clustered within 6 regions of constraint.

DISCUSSION

Our study shows that looking for a combination of paroxysmal events, hyperkinesia, neuropsychiatric symptoms, and cognitive impairment and evaluating the CADD score and variant location can help identify an ATP1A3-related condition, rather than applying diagnostic criteria alone.

Comprehensive Exonic Sequencing of Hemiplegic Migraine-Related Genes in a Cohort of Suspected Probands Identifies Known and Potential Pathogenic Variants

Hemiplegic migraine (HM) is a rare migraine disorder with aura subtype including temporary weakness and visual, sensory, and/or speech symptoms. To date, three main genes—CACNA1A, ATP1A2, and SCN1A—have been found to cause HM. These encode ion channels or transporters, important for regulating neuronal ion balance and synaptic transmission, leading to HM being described as a channelopathy. However, <20% of HM cases referred for genetic testing have mutations in these genes and other genes with roles in ion and solute transport, and neurotransmission has also been implicated in some HM cases. In this study, we performed whole exome sequencing for 187 suspected HM probands referred for genetic testing, but found to be negative for CACNA1A, ATP1A2, and SCN1A mutations, and applied targeted analysis of whole exome sequencing data for rare missense or potential protein-altering variants in the PRRT2, PNKD, SLC1A3, SLC2A1, SLC4A4, ATP1A3, and ATP1A4 genes. We identified known mutations and some potentially pathogenic variants in each of these genes in specific cases, suggesting that their screening improves molecular diagnosis for the disorder. However, the majority of HM patients were found not to have candidate mutations in any of the previously reported HM genes, suggesting that additional genetic factors contributing to the disorder are yet to be identified.

Alternating Hemiplegia of Childhood in Korea: a Case Report

Alternating hemiplegia of childhood (AHC) is a rare neurodevelopmental disorder characterized by recurrent paroxysmal hemiplegic attacks that affect one or the other side of the body. Up to 74% of patients with AHC have a pathologic variant in the ATP1A3 gene. After the introduction of next-generation sequencing, intermediate cases and atypical cases have expanded the clinical spectrum of ATP1A3-related disorders. Herein, we report the first case of AHC in Korea. A 33-year-old man visited our hospital with recurrent hemiplegic and dystonic episode after his first birthday. He was completely normal between episodes and did not have any ataxia, but brain magnetic resonance imaging showed cerebellar atrophy. He also had pes planovalgus deformity. Whole exome sequencing revealed a heterozygous G947R variant in the ATP1A3 gene (c.2839G > C, rs398122887), which is a known pathologic variant. This atypical case of AHC demonstrates the importance of the clinical approach in diagnosing ATP1A3-related disorders.

Hypothermia-induced dystonia and abnormal cerebellar activity in a mouse model with a single disease-mutation in the sodium-potassium pump

Mutations in the neuron-specific α₃ isoform of the Na⁺/K⁺-ATPase are found in patients suffering from Rapid onset Dystonia Parkinsonism and Alternating Hemiplegia of Childhood, two closely related movement disorders. We show that mice harboring a heterozygous hot spot disease mutation, D801Y (α₃^+/D801Y), suffer abrupt hypothermia-induced dystonia identified by electromyographic recordings. Single-neuron in vivo recordings in awake α₃^+/D801Y mice revealed irregular firing of Purkinje cells and their synaptic targets, the deep cerebellar nuclei neurons, which was further exacerbated during dystonia and evolved into abnormal high-frequency burst-like firing. Biophysically, we show that the D-to-Y mutation abolished pump-mediated Na⁺/K⁺ exchange, but allowed the pumps to bind Na⁺ and become phosphorylated. These findings implicate aberrant cerebellar activity in α₃ isoform-related dystonia and add to the functional understanding of the scarce and severe mutations in the α₃ isoform Na⁺/K⁺-ATPase.

The neurological spectrum associated with mutations in the ATP1A3 gene, encoding the α₃ isoform of the Na⁺/K⁺-ATPase, is complex and still poorly understood. To elucidate the disease-specific pathophysiology, we examined a mouse model harboring the mutation D801Y, which was originally found in a patient with Rapid onset Dystonia Parkinsonism, but recently, also in a patient with Alternating Hemiplegia of Childhood. We found that this model exhibited motor deficits and developed dystonia when exposed to a drop in body temperature. Cerebellar in vivo recordings in awake mice revealed irregular firing of Purkinje cells and their synaptic targets, the deep cerebellar nuclei neurons, which was further exacerbated and evolved into abnormal high-frequency burst firing during dystonia. The development of specific neurological features within the ATP1A3 mutation spectrum, such as dystonia, are thought to reflect the functional consequences of each mutation, thus to investigate the consequence of the D801Y mutations we characterized mutated D-to-Y Na⁺/K⁺-ATPases expressed in Xenopus oocytes. These in vitro studies showed that the D-to-Y mutation abolishes pump-mediated Na⁺/K⁺ exchange, but still allows the pumps to bind Na⁺ and become phosphorylated, trapping them in conformations that instead support proton influx.

Recognizable facial features in patients with alternating hemiplegia of childhood

Alternating hemiplegia of childhood is an early onset neurodevelopmental disorder characterized by paroxystic episodes of alternating hemiplegia, variable degrees of intellectual disability, and dystonic movements. The main causative gene, ATP1A3, is also responsible for other neurodevelopmental disorders. While the neurological profile of this condition is well defined, the question whether a recognizable pattern of physical anomalies does exist in this condition is still open. We performed a morphological evaluation of 30 patients at different ages. All patients were evaluated independently by each author and evaluation sheets were compared, discussed, and agreed afterwards. This study started before the identification of ATP1A3 as the causative gene, and the patients were selected upon their neurological picture. Four of these 30 patients tested negative for ATP1A3 mutations and were excluded from the present work. On physical ground, almost all patients shared a similar physical phenotype consisting of hypotonia, long face, thin eyebrows, strabismus, hypertelorism, long palpebral fissures, downturned mouth, and slender habitus. Such phenotype is sufficiently typical to generate a recognizable gestalt. We also evaluated patients photographs taken from the parents in early childhood (6-20 months) to delineate a clinical profile possibly recognizable before the neurological signs suggest the diagnosis. Our data suggest that the typical early gestalt is sufficient to advise the molecular analysis of ATP1A3, even in absence of the pathognomonic neurological signs. Finally, since a number of patients is now adult, some information can be drawn on the phenotypic evolution of the facial appearance of patients with alternating hemiplegia of childhood. © 2016 Wiley Periodicals, Inc.

[ATP1A3 gene mutations in patients with alternating hemiplegia of childhood]

OBJECTIVE

To analyze the ATP1A3 mutations in patients with alternating hemiplegia of childhood (AHC) and recognize its value in diagnosing atypical cases.

METHOD

Data of all AHC patients seen at Peking University First Hospital from August 2005 to November 2014 were prospectively collected. Clinical information of the AHC patients and their family members were collected and analyzed. Genomic DNAs were extracted from their peripheral blood. Mutations in ATP1A3 were screened by Sanger sequencing after PCR.

RESULT

A total of 78 AHC patients were recruited, including 50 males and 28 females. Only three patients had family history of AHC. The first family case had affected mother with AHC; the second family case was the older one of a monozygotic male twins with AHC but their parents were normal; the third family case had a sister with AHC but their parents were normal. The age of onset ranged from six hours to eight years and six months (median: 4 months). According to the Aicardi's clinical diagnostic criteria, 72 patients were considered as typical AHC cases and the other six patients were considered as atypical AHC cases for their age of onset was older than 18 months. Twenty-seven different missense ATP1A3 mutations were detected in 71 (91.0%, 71/78) patients with AHC, including 66 typical and 5 atypical cases. 11 novel ATP1A3 mutations were first reported. ATP1A3 mutations were identified in the three AHC cases with family history. Parental analysis verified that the ATP1A3 mutation of 63 patients (95.5%, 63/66) were de novo origin except lack of five unavailable maternal or paternal genomic DNA. Mutation D801N was found in 20 cases (28.2%), and E815K in 12 cases (16.9%). In the six atypical AHC patients, ATP1A3 mutations were detected in five of them.

CONCLUSION

ATP1A3 was the major causative gene of AHC, and mutations were identified as de novo mostly. ATP1A3 mutations in AHC had mutational hotspot, and the most common mutations were D801N and E815K. ATP1A3 mutation screening is helpful for the genetic and definite diagnosis of the atypical AHC cases.

Alternating Hemiplegia of Childhood: Retrospective Genetic Study and Genotype-Phenotype Correlations in 187 Subjects from the US AHCF Registry

Mutations in ATP1A3 cause Alternating Hemiplegia of Childhood (AHC) by disrupting function of the neuronal Na+/K+ ATPase. Published studies to date indicate 2 recurrent mutations, D801N and E815K, and a more severe phenotype in the E815K cohort. We performed mutation analysis and retrospective genotype-phenotype correlations in all eligible patients with AHC enrolled in the US AHC Foundation registry from 1997-2012. Clinical data were abstracted from standardized caregivers’ questionnaires and medical records and confirmed by expert clinicians. We identified ATP1A3 mutations by Sanger and whole genome sequencing, and compared phenotypes within and between 4 groups of subjects, those with D801N, E815K, other ATP1A3 or no ATP1A3 mutations. We identified heterozygous ATP1A3 mutations in 154 of 187 (82%) AHC patients. Of 34 unique mutations, 31 (91%) are missense, and 16 (47%) had not been previously reported. Concordant with prior studies, more than 2/3 of all mutations are clustered in exons 17 and 18. Of 143 simplex occurrences, 58 had D801N (40%), 38 had E815K (26%) and 11 had G937R (8%) mutations. Patients with an E815K mutation demonstrate an earlier age of onset, more severe motor impairment and a higher prevalence of status epilepticus. This study further expands the number and spectrum of ATP1A3 mutations associated with AHC and confirms a more deleterious effect of the E815K mutation on selected neurologic outcomes. However, the complexity of the disorder and the extensive phenotypic variability among subgroups merits caution and emphasizes the need for further studies.

Chemical chaperone treatment reduces intracellular accumulation of mutant collagen IV and ameliorates the cellular phenotype of a COL4A2 mutation that causes haemorrhagic stroke

Haemorrhagic stroke accounts for ∼20% of stroke cases and porencephaly is a clinical consequence of perinatal cerebral haemorrhaging. Here, we report the identification of a novel dominant G702D mutation in the collagen domain of COL4A2 (collagen IV alpha chain 2) in a family displaying porencephaly with reduced penetrance. COL4A2 is the obligatory protein partner of COL4A1 but in contrast to most COL4A1 mutations, the COL4A2 mutation does not lead to eye or kidney disease. Analysis of dermal biopsies from a patient and his unaffected father, who also carries the mutation, revealed that both display basement membrane (BM) defects. Intriguingly, defective collagen IV incorporation into the dermal BM was observed in the patient only and was associated with endoplasmic reticulum (ER) retention of COL4A2 in primary dermal fibroblasts. This intracellular accumulation led to ER stress, unfolded protein response activation, reduced cell proliferation and increased apoptosis. Interestingly, the absence of ER retention of COL4A2 and ER stress in cells from the unaffected father indicate that accumulation and/or clearance of mutant COL4A2 from the ER may be a critical modifier for disease development. Our analysis also revealed that mutant collagen IV is degraded via the proteasome. Importantly, treatment of patient cells with a chemical chaperone decreased intracellular COL4A2 levels, ER stress and apoptosis, demonstrating that reducing intracellular collagen accumulation can ameliorate the cellular phenotype of COL4A2 mutations. Importantly, these data highlight that manipulation of chaperone levels, intracellular collagen accumulation and ER stress are potential therapeutic options for collagen IV diseases including haemorrhagic stroke.

Alternating hemiplegia of childhood-related neural and behavioural phenotypes in Na+,K+-ATPase α3 missense mutant mice

Missense mutations in ATP1A3 encoding Na⁺,K⁺-ATPase α3 have been identified as the primary cause of alternating hemiplegia of childhood (AHC), a motor disorder with onset typically before the age of 6 months. Affected children tend to be of short stature and can also have epilepsy, ataxia and learning disability. The Na⁺,K⁺-ATPase has a well-known role in maintaining electrochemical gradients across cell membranes, but our understanding of how the mutations cause AHC is limited. Myshkin mutant mice carry an amino acid change (I810N) that affects the same position in Na⁺,K⁺-ATPase α3 as I810S found in AHC. Using molecular modelling, we show that the Myshkin and AHC mutations display similarly severe structural impacts on Na⁺,K⁺-ATPase α3, including upon the K⁺ pore and predicted K⁺ binding sites. Behavioural analysis of Myshkin mice revealed phenotypic abnormalities similar to symptoms of AHC, including motor dysfunction and cognitive impairment. 2-DG imaging of Myshkin mice identified compromised thalamocortical functioning that includes a deficit in frontal cortex functioning (hypofrontality), directly mirroring that reported in AHC, along with reduced thalamocortical functional connectivity. Our results thus provide validation for missense mutations in Na⁺,K⁺-ATPase α3 as a cause of AHC, and highlight Myshkin mice as a starting point for the exploration of disease mechanisms and novel treatments in AHC.

Alternating hemiplegia of childhood

Alternating hemiplegia of childhood (AHC) is a very rare disease characterized by recurrent attacks of loss of muscular tone resulting in hypomobility of one side of the body. The etiology of the disease due to ATP1A3 gene mutations in the majority of patients. Few familial cases have been described. AHC has an onset in the first few months of life. Hemiplegic episodes are often accompanied by other paroxysmal manifestations, such as lateral eyes and head deviation toward the hemiplegic side and a very peculiar monocular nystagmus. As the attack progresses, hemiplegia can shift to the other side of the body. Sometimes the attack can provoke bilateral paralysis, and these patients may have severe clinical impairment, with difficulty in swallowing and breathing. Hemiplegic attacks may be triggered by different stimuli, like bath in warm water, motor activity, or emotion. The frequency of attacks is high, usually several in a month or in a week. The duration is variable from a few minutes to several hours or even days. Sleep can stop the attack. Movement disorders such as dystonia and abnormal movements are frequent. Cognitive delay of variable degree is a common feature. Epilepsy has been reported in 50% of the cases, but seizure onset is usually during the third or fourth year of life. Many drugs have been used in AHC with very few results. Flunarizine has the most supportive anecdotal evidence regarding efficacy.

[When genetics matters: an unusual case of left-sided hemiparesis]

We report the case of a 35-year-old woman who has been admitted to our emergency room because of the sudden onset of a left-sided hemiparesis. The physical examination showed disseminated teleangiectases on the upper and lower lip, on the mucosal surface of the tongue and on the skin. The cerebral CT scan presented a right-sided fronto-parietal lesion, more likely an abscess, confirmed on surgical removal. A meticulous family history showed the presence of similar clinical features among several family members, raising the certainty about the presence of the Rendu-Osler-Weber disease. This case is highly instructive in emphasizing the value of taking a careful medical history and how doing it is extremely important in our daily practice.

Neuropsin promotes oligodendrocyte death, demyelination and axonal degeneration after spinal cord injury

Previous studies indicated that the expression of neuropsin, a serine protease, is induced in mature oligodendrocytes after injury to the CNS. The pathophysiology of spinal cord injury (SCI) involves primary and secondary mechanisms, the latter contributing further to permanent losses of function. To explore the role of neuropsin after SCI, histochemical and behavioral analyses were performed in wild-type (WT) and neuropsin-deficient (neuropsin(-/-)) mice using a crush injury model, a well-characterized and consistently reproducible model of SCI. In situ hybridization revealed that neuropsin mRNA expression was induced in the spinal cord white matter from WT mice after crush SCI, peaking at day 4. Neuropsin(-/-) mice showed attenuated demyelination, oligodendrocyte death, and axonal damage after SCI. Although axonal degeneration in the corticospinal tract was obvious caudal to the lesion site in both strains of mice after SCI, the number of surviving nerve fibers caudal to the lesion was significantly larger in neuropsin(-/-) mice than WT mice. Behavioral analysis revealed that the recovery at days 10-42 was significantly improved in neuropsin(-/-) mice compared with WT mice in spite of the severe initial hindlimb impairments due to SCI in both strains. These observations suggest that neuropsin is involved in the secondary phase of the pathogenesis of SCI mediated by demyelination, oligodendrocyte death, and axonal degeneration.

COL4A1 mutation in a patient with sporadic, recurrent intracerebral hemorrhage

BACKGROUND AND PURPOSE

Recently COL4A1, a gene encoding the type IV collagen alpha1 chain, has been found to be involved in families with autosomal-dominant porencephaly and infantile hemiparesis. In addition to neonatal stroke, some family members had experienced, during adulthood, spontaneous intracerebral hemorrhages (ICHs) and leukoencephalopathy, suggestive of underlying small-vessel disease of the brain. We now report a patient with sporadic, recurrent ICHs and a novel COL4A1 mutation.

METHODS

We performed a clinical and genetic study of a 25-year-old-patient with an 8-year history of recurrent ICHs.

RESULTS

This young, normotensive patient with a history of infantile hemiparesis had experienced, since the age of 17, recurrent, spontaneous, deep ICHs occurring during sports activities. He became severely disabled. Brain magnetic resonance imaging showed ventricular enlargement, diffuse white-matter abnormalities, and newly appearing, deep, silent microbleeds. Extensive investigations found no cause. There was no family history of stroke or infantile hemiparesis. A novel COL4A1 mutation (G805R) was identified.

CONCLUSIONS

The clinical spectrum of COL4A1 mutations includes recurrent ICHs in association with diffuse leukoencephalopathy in young adults, even in the absence of a family history of infantile hemiparesis or ICH. In addition to birth trauma, anticoagulant use, and head trauma previously reported, sports activities may be a precipitating factor of ICHs in persons with COL4A1 mutations.

The genetic spectrum of a population-based sample of familial hemiplegic migraine

Familial hemiplegic migraine (FHM) is a rare subtype of migraine with aura and transient hemiplegia. FHM mutations are known in three genes, the CACNA1A (FHM1) gene, the ATP1A2 (FHM2) and the SCN1A (FHM3) gene and seem to have an autosomal-dominant mode of inheritance. The aim of this study was to search for FHM mutations in FHM families identified through a screen of the Danish population of 5.2 million people. FHM patients were diagnosed according to the International Classification of Headache Disorders and all FHM patients had a physical and neurological examination by a physician. A total of 147 FHM patients from 44 different families were identified; 43 FHM families participated in this study. Linkage analysis of these families shows clear linkage to the FHM locus (FHM1) on chromosome 19, supportive linkage to the FHM2 locus whereas no linkage was found to the FHM3 locus. Furthermore, we sequenced all exons and promoter regions of the CACNA1A and ATP1A2 genes and screened for the Q1489K mutation in the SCN1A gene. CACNA1A gene mutations were identified in three of the FHM families, two known FHM mutations, R583Q and T666M and one novel C1369Y mutation. Three FHM families were identified with novel mutations in the ATP1A2 gene; a family with a V138A mutation, a family with a R202Q mutation and a family with a R763C mutation. None of the Danish FHM families have the Q1489K mutation in the SCN1A gene. Our study shows that only 14% (6/42) of FHM families in the general Danish population have exonic FHM mutations in the CACNA1A or ATP1A2 gene. The families we identified with FHM mutations in the CACNA1A and ATP1A2 genes were extended, multiple affected families whereas the remaining FHM families were smaller. The existence of many small families in the Danish FHM cohort may reflect less bias in FHM family ascertainment and/or more locus heterogeneity than described previously.

Alternating hemiplegia of childhood: no mutations in the glutamate transporter EAAT1

Alternating hemiplegia of childhood (AHC) is a severe brain disorder, mainly characterised by episodes of hemiplegia, progressive mental retardation, and other severe paroxysmal and permanent neurological symptoms. Clinically and genetically, there is some overlap with sporadic (SHM) and familial (FHM) hemiplegic migraine, a severe monogenic subtype of migraine. Although no mutations were detected in the FHM1 CACNA1A and FHM2 ATP1A2 genes in sporadic AHC patients, a mutation was found in the FHM2 ATP1A2 gene in a family with AHC. Recently, a missense mutation was found in the SLC1A3 gene that encodes the glutamate transporter EAAT1, in a patient with alternating hemiplegia, episodic ataxia, seizures, and headache. Because of the remarkable clinical similarities and the potential role of glutamate in AHC, we analysed six sporadic patients with AHC for mutations in the SLC1A3 gene. No mutations were found. The SLC1A3 EAAT1 glutamate transporter gene does not seem to be involved in the pathogenesis of AHC.

Two de novo mutations in the Na,K-ATPase gene ATP1A2 associated with pure familial hemiplegic migraine

Familial hemiplegic migraine (FHM) is a rare autosomal dominantly inherited subtype of migraine, in which hemiparesis occurs during the aura. The majority of the families carry mutations in the CACNA1A gene on chromosome 19p13 (FHM1). About 20% of FHM families is linked to chromosome 1q23 (FHM2), and has mutations in the ATP1A2 gene, encoding the alpha2-subunit of the Na,K-ATPase. Mutation analysis in a Dutch and a Turkish family with pure FHM revealed two novel de novo missense mutations, R593W and V628M, respectively. Cellular survival assays support the hypothesis that both mutations are disease-causative. The identification of the first de novo mutations underscores beyond any doubt the involvement of the ATP1A2 gene in FHM2.

Sporadic and Familial Hemiplegic Migraine: Diagnosis and Treatment

Hemiplegic migraine is a rare subtype of migraine with aura associated with transient hemiplegia. The weakness is caused by motor aura. Hemiplegic migraine is the only headache syndrome associated with known genetic mutations and serves as a model for understanding more common varieties of migraine. Because the phenotype includes striking yet transient neurological signs and symptoms, it is imperative that clinicians know the differential diagnosis to rule out possible secondary etiologies when treating patients with hemiplegic spells. Hemiplegic migraine occurs with equal prevalence in either a sporadic or familial form differentiated only by family history. Thus far, treatment trials are anecdotal, although verapamil and acetazolamide have shown promise.

Nonprogressive familial leukoencephalopathy with porencephalic cyst and focal seizures

Two siblings with a similar white-matter disease but different clinical symptoms are described. The first sibling suffers from nonprogressive spastic hemiparesis secondary to a congenital periventricular porencephalic cyst. Her brother has focal epilepsy. On magnetic resonance imaging, both patients show diffuse white-matter involvement predominantly of the posterior periventricular area. We suggest that this is a familial white-matter disorder with minimal symptoms and no progression in early childhood.

Opening of the blood-brain barrier preceding cortical edema in a severe attack of FHM type II

The authors report a patient with familial hemiplegic migraine type II who developed a long-lasting attack including fever, right-sided hemiplegia, aphasia, and coma. Quantitative analysis of early gadolinium-enhanced MRI revealed a mild but significant left-hemispheric blood-brain barrier (BBB) opening limited to the cortex and preceding cortical edema. The findings suggest that the delayed cortical edema was vasogenic in the severe migraine aura variant of this ATP1A2 mutation carrier.

1H-MRS alterations in the cerebellum of patients with familial hemiplegic migraine type 1

BACKGROUND

About 20% of patients with familial hemiplegic migraine (FHM) develop progressive cerebellar signs. Genetic studies have established an association with mutations in the CACNA1A gene. However, the mechanisms underlying cerebellar involvement are largely unknown.

OBJECTIVE

To use proton MR spectroscopy (1H-MRS) to investigate metabolic alterations in the cerebellum as well as cortical regions known to be involved in the propagation of migraine aura.

METHODS

Fifteen CACNA1A mutation carriers from three FHM families and 17 healthy control subjects were studied. Eleven patients had clinical signs of cerebellar involvement. LCModel fits were used to estimate absolute concentrations of N-acetyl aspartate (NAA), myo-inositol (mI), glutamate (Glu), choline-containing compounds, total creatine, and lactate in the superior cerebellar vermis (SCV), parietal cortex, and occipital cortex. To control for atrophy effects, automated image segmentation was performed using SPM99. The brain parenchyma fraction (BPF) was determined for all three regions.

RESULTS

Compared with controls, the brain parenchyma fraction (BPF), NAA, and Glu were significantly reduced and mI was significantly elevated in the SCV of patients with FHM. In contrast, no metabolite alterations were found in supratentorial regions. BPF and NAA in the SCV significantly correlated with cerebellar scores, in particular, gait ataxia.

CONCLUSIONS

The findings suggest that there is a regionally distinct neuronal impairment in the superior cerebellar vermis that exceeds macroscopic tissue loss. Correlations with clinical scores emphasize the functional relevance of localized atrophy (brain parenchyma fraction) and N-acetyl aspartate levels. These measures may be useful to monitor disease progression. The observed reduction in glutamate may in part reflect impaired glutamatergic neurotransmission.

Functional effects of Na+,K+-ATPase gene mutations linked to familial hemiplegic migraine

Familial hemiplegic migraine type 2, an autosomal dominant form of migraine with aura, has been associated with four distinct mutations in the alpha2-subunit of the Na+,K+-ATPase. We have introduced these mutations in the alpha2-subunit of the human Na+,K+-ATPase and the corresponding mutations in the Bufo marinus alpha1-subunit and studied these mutants by expression in Xenopus oocyte. Metabolic labeling studies showed that the mutants were synthesized and associated with the beta-subunit, except for the alpha2HW887R mutant, which was poorly synthesized, and the alpha1BW890R, which was partially retained in the endoplasmic reticulum. [3H]ouabain binding showed the presence of the alpha2HR689Q and alpha2HM731T at the membrane, whereas the alpha2HL764P and alpha2HW887R could not be detected. Functional studies with the mutants of the B. marinus Na+,K+-ATPase showed a reduced or abolished electrogenic activity and a low K+ affinity for the alpha1BW890R mutant. Through different mechanisms, all these mutations result in a strong decrease of the functional expression of the Na+,K+-pump. The decreased activity in alpha2 isoform of the Na+,K+-pump expressed in astrocytes seems an essential component of hemiplegic migraine pathogenesis and may be responsible for the cortical spreading depression, which is one of the first events in migraine attacks.

Prenatal stroke in a neonate heterozygous for factor V Leiden mutation

The authors report an infant with congenital hemiplegia associated to heterozygosity for factor V Leiden. Prenatal stroke in the left cerebral hemisphere was diagnosed by ultrasonography at the 28th week of pregnancy, and followed up until birth. Although neonatal neurologic examination was normal, a moderate right hemiparesis developed along the 1st months of life. Coagulation studies performed in the neonatal period and at the age of 18 months revealed activated protein C resistance due to factor V Leiden mutation (R506Q). There are some previous reports of stroke associated to this mutation in near or at term neonates, but to our knowledge this is the stroke detected at the most early stage of fetal development.

Mutation in the neuronal voltage-gated sodium channel SCN1A in familial hemiplegic migraine

BACKGROUND

Familial hemiplegic migraine is an autosomal dominant severe subtype of migraine with aura characterised by some degree of hemiparesis during the attacks. So far, mutations in two genes regulating ion translocation-CACNA1A and ATP1A2-have been identified in pedigrees with this disease.

METHODS

To identify additional genes for familial hemiplegic migraine, we did a genome-wide linkage analysis of two disease pedigrees without mutations in CACNA1A and ATP1A2. Ion channel genes in the candidate interval were analysed for mutations, and the functional consequences of the recorded sequence alteration were determined.

FINDINGS

We identified a novel locus for familial hemiplegic migraine on chromosome 2q24. Sequencing of candidate genes in this region revealed a heterozygous missense mutation (Gln1489Lys) in the neuronal voltage-gated sodium channel gene SCN1A, mutations of which have been associated with epilepsy. This same mutation was present in three families with familial hemiplegic migraine. It results in a charge-altering aminoacid exchange in the so-called hinged-lid domain of the protein, which is critical for fast inactivation of the channel. Whole-cell recordings in transiently transfected tsA201 cells expressing the highly homologous SCN5A sodium channel showed that the mutation induces a two-fold to four-fold accelerated recovery from fast inactivation without altering any of the other channel parameters investigated.

INTERPRETATION

Dysfunction of the neuronal sodium channel SCN1A can cause familial hemiplegic migraine. Our findings have implications for the understanding of migraine aura. Moreover, our study reinforces the molecular links between migraine and epilepsy, two common paroxysmal disorders.

Alterations in the alpha2 isoform of Na,K-ATPase associated with familial hemiplegic migraine type 2

A number of missense mutations in the Na,K-ATPase alpha2 catalytic subunit have been identified in familial hemiplegic migraine with aura. Two alleles (L764P and W887R) showed loss-of-function, whereas a third (T345A) is fully functional but with altered Na,K-ATPase kinetics. This study describes two additional mutants, R689Q and M731T, originally identified by Vanmolkot et al. [Vanmolkot, K. R., et al. (2003) Ann. Neurol. 54, 360-366], which we show here to also be functional and kinetically altered. Both mutants have reduced catalytic turnover and increased apparent affinity for extracellular K(+). For both R689Q and M731T, sensitivity to vanadate inhibition is decreased, suggesting that the steady-state E(1) <==> E(2) poise of the enzyme is shifted toward E(1). Whereas the K'(ATP) is not affected by the R689Q replacement, the M731T mutant has an increase in apparent affinity for ATP. Analysis of the structural changes effected by T345A, R689Q, and M731T mutations, based on homologous replacements in the known crystal structure of the sarcoplasmic reticulum Ca-ATPase, provides insights into the molecular bases for the kinetic alterations. It is suggested that the disease phenotype is the consequence of lowered molecular activity of the alpha2 pump isoform due to either decreased K(+) affinity (T345A) or catalytic turnover (R689Q and M731T), thus causing a delay in extracellular K(+) clearance and/or altered localized Ca(2+) handling/signaling secondary to reduced activity in colocalized Na(+)/Ca(2+) exchange.

Mutation in the glutamate transporter EAAT1 causes episodic ataxia, hemiplegia, and seizures

BACKGROUND

Transporters, ion pumps, and ion channels are membrane proteins that regulate selective permeability and maintain ionic gradients across cell membranes. Mutations in CACNA1A encoding a neuronal calcium channel and ATP1A2 encoding an ion pump cause episodic ataxia, hemiplegic migraine, and seizures. Mutant gene products of both CACNA1A and ATP1A2 may affect neurotransmission of glutamate, the most abundant excitatory amino acid neurotransmitter.

METHODS

We examined our patient population with episodic ataxia and hemiplegic migraine but with no mutation in either CACNA1A or ATP1A2. We looked for mutations in SLC1A3, which encodes the glutamate transporter excitatory amino acid transporter (EAAT) 1 that is important in removing glutamate from the synaptic cleft.

RESULTS

A patient with episodic ataxia, seizures, migraine, and alternating hemiplegia has a heterozygous mutation in SLC1A3 that is not present in his asymptomatic parents and controls. Expression studies of the mutant EAAT1 showed decreased expression of the protein with a markedly reduced capacity for glutamate uptake. When coexpressed, the mutant EAAT1 decreased the activity of wild-type EAAT1 but not of two other transporters EAAT2 or EAAT3, suggesting that mutant EAAT1 specifically multimerizes with wild-type EAAT1 to exert its dominant negative effect.

CONCLUSION

Our data show that a heterozygous mutation in EAAT1 can lead to decreased glutamate uptake, which can contribute to neuronal hyperexcitability to cause seizures, hemiplegia, and episodic ataxia.

Childhood neurological presentation of a novel mitochondrial tRNA(Val) gene mutation

We describe a young girl with a novel 1659T>C mutation in the tRNA(Val) gene of mitochondrial DNA (mtDNA) who presented with learning difficulties, hemiplegia, and a movement disorder, together with a raised cerebrospinal fluid (CSF) lactate. The mutation, which was present at high levels of heteroplasmy in patient tissues, interrupts a conserved Watson-Crick basepair in the TPsiC stem and has not previously been described in controls. This report further confirms the frequent association of mitochondrial tRNA mutation with neurological presentations, even in paediatric cases.

Familial Hemiplegic Migraine Type 1 Mutations K1336E, W1684R, and V1696I Alter Cav2.1 Ca2+ Channel Gating

Mutations in the Cav2.1 alpha1-subunit of P/Q-type Ca2+ channels cause human diseases, including familial hemiplegic migraine type-1 (FHM1). FHM1 mutations alter channel gating and enhanced channel activity at negative potentials appears to be a common pathogenetic mechanism. Different beta-subunit isoforms (primarily beta4 and beta3) participate in the formation of Cav2.1 channel complexes in mammalian brain. Here we investigated not only whether FHM1 mutations K1336E (KE), W1684R (WR), and V1696I (VI) can affect Cav2.1 channel function but focused on the important question whether mutation-induced changes on channel gating depend on the beta-subunit isoform. Mutants were co-expressed in Xenopus oocytes together with beta1, beta3, or beta4 and alpha2delta1 subunits, and channel function was analyzed using the two-electrode voltage-clamp technique. WR shifted the voltage dependence for steady-state inactivation of Ba2+ inward currents (IBa) to more negative voltages with all beta-subunits tested. In contrast, a similar shift was observed for KE only when expressed with beta3. All mutations promoted IBa decay during pulse trains only when expressed with beta1 or beta3 but not with beta4. Enhanced decay could be explained by delayed recovery from inactivation. KE accelerated IBa inactivation only when co-expressed with beta3, and VI slowed inactivation only with beta1 or beta3. KE and WR shifted channel activation of IBa to more negative voltages. As the beta-subunit composition of Cav2.1 channels varies in different brain regions, our data predict that the functional FHM1 phenotype also varies between different neurons or even within different neuronal compartments.

Variability of familial hemiplegic migraine with novel A1A2 Na+/K+-ATPase variants

A1A2 Na+/K+-ATPase mutations cause familial hemiplegic migraine type 2 (FHM2). The authors identified three putative A1A2 mutations (D718N, R763H, P979L) and three that await validation (P796R, E902K, X1021R). Ten to 20% of FHM cases may be FHM2. A1A2 mutations have a penetrance of about 87%. D718N causes frequent, long-lasting HM, and P979L may cause recurrent coma. D718N and P979L may predispose to seizures and mental retardation. A1A2 does not play a major role in sporadic HM; only one variant, R383H, occurred in 1 of 24 cases.

Kinetic Alterations due to a Missense Mutation in the Na,K-ATPase α2 Subunit Cause Familial Hemiplegic Migraine Type 2

A number of missense mutations in the ATP1A2 gene, which encodes the Na,K-ATPase alpha2 subunit, have been identified in familial hemiplegic migraine with aura. Loss of function and haploinsufficiency have been the suggested mechanisms in mutants for which functional analysis has been reported. This paper describes a kinetic analysis of mutant T345A, recently identified in a detailed genetic analysis of a large Finnish family (Kaunisto, M. A., Harno, H., Vanmolkot, K. R., Gargus, J. J., Sun, G., Hamalainen, E., Liukkonen, E., Kallela, M., van den Maagdenberg, A. M., Frants, R. R., Farkkila, M., Palotie, A., and Wessman, M. (2004) Neurogenetics 5, 141-146). Introducing T345A into the conserved rat alpha2 enzyme does not alter cell growth or catalytic turnover but causes a substantial decrease in apparent K+ affinity (2-fold increase in K0.5(K+)). In view of the location of Thr-345 in the cytoplasmic stalk domain adjacent to transmembrane segment 4, the 2-fold increase in K0.5(K+) is probably due to T345A replacement altering K+ occlusion/deocclusion. Faster K+ deocclusion of the mutant via the E2(K) + ATP --> E1.ATP + K+ partial reaction is evidenced in (i) a marked increase (300%) in K+ stimulation of Na-ATPase at micromolar ATP, (ii) a 4-fold decrease in KATP, and (iii) only a modest increase (approximately 3-fold) in I50 for vanadate, which was used as a probe of the steady state E1/E2 conformational equilibrium. We suggest that the decreased apparent K+ affinity is the basis for a reduced rate of extracellular K+ removal, which delays the recovery phase of nerve impulse transmission in the central nervous system and, thereby, the clinical picture of migraine with aura. This is the first demonstration of a mutation that leads to a disease associated with a kinetically altered but fully functional Na,K-ATPase, refining the molecular mechanism of pathogenesis in familial hemiplegic migraine.

Alternating hemiplegia of childhood: no mutations in the second familial hemiplegic migraine gene ATP1A2

Alternating hemiplegia of childhood (AHC) is a rare disorder mainly characterised by attacks of hemiplegia and mental retardation. AHC has often been associated with migraine. Previously, we have excluded the involvement of the familial hemiplegic migraine (FHM) CACNA1A gene in four patients with AHC. A second gene for FHM was discovered recently: the ATP1A2 gene on chromosome 1q23, coding for the alpha 2 subunit of Na+,K+-ATPase. We performed a mutation analysis of the ATP1A2 gene in six patients, using direct sequencing, but found no mutations in any of the 23 exons. Other cerebral ion channel genes remain candidate genes for AHC.

Muscle molecular phenotype after stroke is associated with gait speed

The disability of patients after stroke is generally attributed to upper motor neuron defects, but secondary changes in paretic muscle may enhance the disability. We analyzed the molecular phenotype and metabolic profile of the paretic and nonparetic vastus lateralis (VL) and we measured the severity of gait deficit in 13 patients at least 6 months after ischemic stroke. The results showed a significant increase in the proportion of fast myosin heavy chain (MHC, 68 +/- 14%) in the paretic compared to the nonparetic VL (50 +/- 13%). The specific activity of citrate synthase and glyceraldehyde phosphodehydrogenase was not significantly different between the two sides. The proportion of fast MHC was inversely associated with severity of gait deficit indexed by self-selected walking speed in the paretic leg, but not the nonparetic leg. Our findings demonstrate significant and potentially modifiable secondary biologic changes in hemiparetic muscle phenotype that may contribute to the disability of stroke.